The medial terminal nucleus (nBOR) of the accessory optic system is a constant component of all vertebrate visual systems, including man. Brauth and Karten (1975, 1976) recently discovered the nBOR projects monosynaptically upon the vestibulo-cerebellum (uvula and flocculonodular lobe) and suggested that it plays a major role in control of eye movement. This application outlines our proposal to identify the retinal ganglion cells projecting upon the nBOR, characterize their morphology, the caliber of anons of the retinal projection to nBOR, study the cytology and histochemistry of the nBOR and pattern of retinal terminations using light and electron microscopy. Developmental studies will attempt to study (a) The time of origin of the nBOR in relation to the time of origin of the retinal ganglion cells, (b) The role of retinal inputs in differentiation of the nBOR. I suggest that the nBOR is concerned with the initial phase of eye-neck movements in response to a peripheral stimulus. Collaborative studies, separate of this proposal, will investigate the electrophysiology and behavioral role of the nBOR.